Tohatsu M40D2 (2006) lower sparkplug WET!!!

[Troutboy NZ]

Lower plug (3 cylinder) only wet with saltwater or fuel - I can't tell, but it tastes salty/sour when I sample the droplets. The engine is running absolutley perfectly so I'm not sure what is causing this, have done compression test and all even across the cylinders 130psi in all, new plugs (lower one still gets soaked with fuel or water). There's no hesitation or idle stumble and it winds out to WOT fine and will run there all day! Everything is smooth and functioning as it should.

I'm stumped to why this lower plug is wet! Can anyone enlighten me to why this is? I can only think of crancase seal or head gasket but this would cause running problems surely - it really does run perfect and this is the second one of these I have had in 5 years with no problems.

Cheers.

 

[JB]

Re: Tohatsu M40D2 (2006) lower sparkplug WET!!!

When you shut off the ignition the spark stops and the crank continues to turn for a few revs. The carbs continue to supply fuel to the air stream until the crank stops. That puts unburned fuel into at least one cylinder.

That could be the reason you find a plug wet, though it is a mystery to me why it is always the same plug.

 

[TOHATSU GURU]

Re: Tohatsu M40D2 (2006) lower sparkplug WET!!!

"Tastes salty" What would Alton Brown say? I would run it by a dealer in New Zealand and let them take a look at it. Weak ignition on that cylinder or a fuel system error on either the carburetor or reeds on that cylinder could give you extra fuel as well. If it is water you could have anything from a cracked block to a leaking gasket.

 

[Troutboy NZ]

Re: Tohatsu M40D2 (2006) lower sparkplug WET!!!

Thanks for the input guys. Tohatsu guru, wouldn't a cracked head / leaking gasket or crankcase seal go hand in hand with running problems? As I am having none what so ever. The engine is certainly running cool, you can hold your hand on the block (just) at operating temp, and cooling water stream is within spec. I can't get to a dealer here for quite a while unfortunatley.

When you say and ignition problem, do you think it is worthwhile swapping over a coil pack to see if that makes one of the other plugs get these black wet moisture deposits on it? The other possibilty is is simply just adjusted too rich on the lower carb I guess, but it does not look like oil.

Thanks again.

 

[TOHATSU GURU]

Re: Tohatsu M40D2 (2006) lower sparkplug WET!!!

Generally yes. There would almost certainly be a degradation due to the water itself as well as probable compression loss. But almost is not the same thing as definite so you can't rule it out at this point. You can swap out on the ignition coils and even do it on the trigger coils, but........Say bye, bye to your warranty if you inadvertently fry one.

The most likely source would be an incorrect carb adjustment. However, when your dealer did the installation and then the subsequebt 10-20 hour check it should have been checked. It will not change on it's own.

 

[Troutboy NZ]

Re: Tohatsu M40D2 (2006) lower sparkplug WET!!!

Thanks for that, in the interim I'll try a very precisley measured tweak of the lower carb adjustment screw to lean it out a 1/4 of a turn to see if that makes any difference until I can get it to a dealer. I presume it is turn IN to lean and turn OUT to richen on Tohatsu as they are not air-bleed screws?